Welder control system



NOV 13, 1951 H. 1. sTANBAcK ETAL WELDER CONTROL SYSTEM Filed March 8,1949 2 SHEETS-SHEET 1 n. jm i y 6. d i5 FB NOV- 13, 1951 H. l. sTANBAckET AL WELDER CONTROL SYSTEM 2 SHEETS--SHEET 2 Filed March 8, 1949Patented Nov. 13, 1951 WELDER CONTROL SYSTEM Harris I. Stanback,Milwaukee, and Ernest G. Anger, Wauwatosa, Wis., assignors to Square DCompany, Detroit, Mich., a corporation of Michigan Application March 8,1949, Serial No. 80,118

(Cl. B19- 4) 18 Claims.

This invention relates to a control system for electric welding and hasfor its object the provision of an improved form of such control systemwhich is fully electronic in operation except for the initially operatedcontrol switch.

Another object of the invention is the provision of an electric controlsystem having improved system arrangements for the determination ofsqueeze weld," hold and oli times which constitute improvements in theart both individually and in combination, each with any one or all ofthe others.

Another object of the invention is the provision of an electric Weldercontrol system in accordance with the preceding object in which theinitiation and termination of the timing periods is determinedelectronically Without the interposition of intermediate control relays.

Other objects and features of the invention Will be readily apparent tothose skilled in the art from the specification and appended drawingsillustrating certain preferred embodiments inwhich:

Figures 1 and 2 combined form a schematic Wiring diagram of the electricWelder control system according to the present invention.

The charging arrangement for the ring capacitors of the discharge tubesis described and claimed in a copending application of Ernest G. Angerentitled Firing of Electric Discharge Tubes filed March 2, 1949, SerialNo. 79,149, now abandoned.

Certain circuit arrangements preventing the build-up of dangerously highvoltages in the standby condition are described and claimed inapplicants copending application entitled Firing System for ElectricDischarge Tubes filed March 2, 1949, Serial No. 79,214, now U. S. Patent2,520,478 granted August 29, 1950.

The system arrangement to secure proper leadtrail tube characteristicand the polarizing of the initial weld current is described and claimedin applicants copending application entitled Lead Trail Control Systemfor Electric Discharge Tubes led March 2, 1949, Serial No. 79,212, nowU. S. Patent 2,520,477 granted August 29, 1950.

The safety feature of the system in the connection of the heater coilsfor the thermal now switches is described and claimed in a copendingapplication of Harris I. Stanback entitled Overheating Safety `Systemfor Electric Discharge Tubes and iiled March 2, 1949, Serial No. 79,211,now U. S. Patent 2,520,476 granted August 29, 1950.

The timing control for the weld time is de- 2 scribed and claimed inapplicants copending application entitled Electrical Timing Controlfiled March 2, 1949, Serial No. 79 213, now U. S. Patent 2,534,385granted December 19, 1950.

In the system as illustrated in the diagram, the mains I and 2 of Figure2 are connected t0 a source of alternating voltage and serve to supplypower to the load and controlling circuits. A voltage reducingtransformer 3 supplies the control lines 4, 5. Transformer 5 of Figure1, Whose primary is energized across the lines 4 and 5, provides energyto a full wave rectifier bridge 1 the output of which supplies a D. C.potential across the lines 8 and 5. A capacitor 9. resistor II and avoltage regulator tube I2 aid in maintaining a constant D. C. potential.

The rectier bridge I supplies the duplex valve I3, I3a and valve I4. Inthe anode circuit of valve I3 is a voltage determining resistor I5; inthe anode circuit of valve I4 is a loading resistor I6. In the gridcircuit of the valve I4 is a capacitor I1 and a parallel adjustableresistor combination I8 connected to the lines 3 and 5 through thevoltage determining resistors I9 and 2 I. Also across the lines 8 and 5is an electric valve 22 through which is charged a capacitor 23, bridgedby an adjustable resistor combination 24, the capacitor connected in thegrid circuit of an electric valve 25, and to the lines 8 and 5 throughvoltage determining resistors 26 and 21. Also in the grid circuit ofelectric valve 25 is an electric valve 28, the conduction of which, uponclosure of a repeat-nonrepeat switch 29A serves to charge the capacitor23 when the valve 25 is nonconducting. A capacitor 3| is provided in thegrid circuit of the electric valve 23 to insure that the valve 28 willnot conduct immediately upon closure of an initiating switch 32, whichwould prevent the conduction of valve 25. In the circuit of valve 25through switch 32 is connected a relay energizing coil 33 which servesto close the contacts 34, 35 and 35 and open the contacts 3l and 38. Avalve solenoid 39 is connected to be energized when the contact 34closes.

A bridge rectier indicated at 4I is supplied by a transformer 42, theprimary of which is energized across the supply lines 4 and 5. Acapacitor 43 and pressure switch 44 are associated with the bridgerectifier 4I and together with the voltage dividing resistors 45 and 46serve to aiiect the potential at the control grid 41 of an electricvalve 48. Also aiecting the potential at the control grid 4'I of theelectric valve 4B is a capacitor 49 and a parallel adjustable resistorcombination 5I. A transformer 52, Whose primary is energized from thesupply lines 4 and 5 after the contact 35 closes, serves to providepotential to the anode and cathode of the electric Valve 48 through arectifier valve 53 and timing capacitors 54 and 55. Connected to thecathode of the electric valve 48 is a capacitor 56 connected so as to becharged from a transformer 51 upon conduction of the electric valve 48.Adjustable resistor combinations 58 and 59 bridge the timing capacitor55 while a tapped resistor 6I and a biasing circuit, consisting of atransformer 82 energized from the supply lines, a rectifier 63, acapacitor 64 and a resistor 65, for the grid 68 of valve 81, areconnected across the timing capacitor 54. ln series with the timing,rcapacitor 54 is the secondary of a synchronizing transformer 88energized from the supply lines 4 and 5. At the tap to the resistor 6|is connected the control grid 68 of an electric valve 61, the cathode 69of which is connected to the negative side of capacitor 55.

A transformer 1! has its primary connected to the supply across lines 4and 5 through contact 36 and its secondary output fed to the anode 12and cathode 89 of the electric valve 51 through the primary oftransformers 13 and 14. The secondary of the transformer 14 is connectedacross the capacitor 'I5 '(see Figure 2) connected in the circuit of thegrid of electric valve 16 which controls the charging of the iiringcapacitor 11.

The rsecondary of the transform-er 13 is connected across a capacitor I8through a rectiiier 19,'the capacitor bridged by a resistor 8| andconnected in the grid circuit of valve I3. The capacitor 18 and resistor8| are also connected between the lines and '8 through a resistor 8.2.

A transformer 83 has its primary energize-d from the mains I and 2 andits secondary connected in thecontrol grid circuit of valve 16 in serieswith the capacitor and a capacitor 84 which is bypassed by a resistor85. The anode and cathode of the valve 16 are connected across thesecondary output of a transformer 86 in series with a firing capacitor11, and with the reactor 81 tuned for series resonance with the ringcapacitor 11. The primary of transformer 86 is energized from the mainsI and 2. Also in series with the circuit of the valve 'ISare the primaryof a transformer 88 and the contacts 89 of a vthermal flow switch forthe electric discharge tubes 9| and |83. Across the ring capacitor 11,which discharges therethrough, is connected the igniter 92 of electricdischarge tube 9| through an electric valve 93. Valve 93 has its grid:94 connected to ahold-ofi` bias circuit comprising the secondary oftransformer 95, a rectier 96, and a capacitor 91 bypassed by resistor98, the primary of transformer 95'being connected across mains I and 2.Also in the circuit of grid 94 is a secondary of peaking transformer 99,the primary of which is connected with an adjustableresistance-capacitance phase shifting network indicated generally atIUI, the resistance |02 being adjustable v'to vary the phase angle ofthe secondary voltage of the transformer 99.

Connected back `to back with the electric discharge tube 9| is a secondtube |83, these discharge tubes serving to pass both halfl cycles ofmain supply current-through the load represented by the primary |84 of awelding transformer |95, the secondary I 06 supplying a welding load at|01. Electric discharge tube |83 is fired by components similar to thoseset forth with respect tok tube 9|, these constituting the iiringcapacitor |88, the discharge valve I 89 and charging 'valve III.

To secure proper firing of the charging valve III, the secondary output0f transformer 88 is fed across a capacitor |I2 in the grid circuit ofvalve III, in series with the elements supplying the hold-off bias andconstituted by the secondary transformer I|3 and the capacitor I|4bypassed by resistor |I5. The capacitor'l I2 is bypassed by a dischargeresistor IIB. In series with the firing capacitor |08 and the valve IIIare the contacts II'I of the thermal flow switch for the discharge tubesand the reactor |24 in series resonance with firing capacitor |98.

The heaters for the thermal flow switches, whose contacts are shown at89 and ||1 are shown at II8 connected in series with each other andthrough the primary of transformer I9 to a tap-oli point of atransformer 3 connected across mains I and 2. The secondary output oftransformer I I9 is fed through the cathode heaters or laments of therectifier tube 53.

The operation of the -system is as follows:

Closure of initiating switch 32 serves to connect across the lines 4 and5, the electric valveL 25 which conducts to energize relay coil 33,which causes, first, the normally closed contact 38 to open, therebyeiectively disconnecting control grid 41 of valve 48 from the positiveD. C. voltage supplied by rectifier bridge 1. The energized relay 33then closes the switch 34 which energizes the valve solenoid 39 on theWelder.; opens the switch 31 which removes the short circuit acrosscapacitor 56; closes the switch 35 which forms a non-beat holdingcircuit in parallel with the initiating switch; and closes the switch 36which energizes supply transformers 1I and 52.

Before contact 38 was opened, capacitor 49 was charged by control gridconduction of valve 48 to the positive Value of the D. C. voltageprovided by the rectier bridge 1. When the contact 38 is opened, thesupply of positive D. C. voltage is no longer directly in contact withcapacitor 49 and the control grid 41 of valve 48 assumes a negativepotential, the value .of which is .determined by the voltagesupplytransformer 42, rectier bridge 4|, capacitor 43,y and voltagedivider resistors 45, 46,. While pressure switch 44 is open, this gridpotential is always suficiently negative to prevent the conduction ofvalve 48.

When the pressure switch 44 closes, however, the charge on capacitor 43is so dissipated that the grid 41 of valve 48 is permitted to becomesucently positive at the beginning of each positive half cycle so thatvalve 48 conducts, providing the previously mentioned charge oncapacitor 49 has been dissipated through the adjustable ble-ederresistor combination 5I. Conduction of valve 48 will not occur,regardless of closing of pressure switch 44, until the charge oncapacitor 49 has been dissipated. The duration of this charge will bedetermined by the setting of bleeder resistor 5| Whose adjustmenttherefor determines the timing interval of the squeeze time inthewelding sequence. When valve 48 conducts, it passes current whichcharges the weld time capacitors -54 and 55 from transformer 52 throughrectier tube 53. The conduction current of valve 48 also -energizestransformer 51, the secondary of which serves tc charge capacitor 53 byscreen grid I2| conduction of Valve 48. The charge built up on thiscapacitor is of such nature as to cause the potential of the cathode |22of valve 48 to become substan-ftia'lly positive with respect to thecontrol grid 41 v of that valve. This charge will prevent the.conduction of vvalve 48 for any 'period in excess of a single halfcycle at the beginning of each system operation, each charge remainingupon the capacitor 56 until relay coil 33 is deenergized and contact 31closed to remove the charge of the capacitor 56.

While valve 48 is conducting, the timing capacitors 54 and 55 arecharged simultaneously to the same voltage and are then effectivelydisconnected from the charging transformer 52 when valve 48 ceasestoconduct. The tap-off point on resistor 6| is connected to the grid 66 ofvalve 61. This tap is so disposed as to place the grid 66 atapproximately one-third the negative potential of capacitor 54. Thecathode 6d, meanwhile, is electrically connected to capacitor 55 and isat the full negative potential of that capacitor. The grid 66 istherefore substantially positive with respect to the cathode t9 andsufficiently so as to effect conduction of valve 61 during those halfcycles during which the anode 12 of the valve 61 is positive withrespect to cathode 69 thereof. Capacitor 54 discharges very slowlythrough resistor 6|; capacitor 55, however, discharges more rapidlythrough adjustable resistor combination 58 and 5S. In eiect, therefore,the potential of cathode 69 approaches that of grid 66, due to the morerapid discharge of capacitor 55, until the potentials or" the cathodeand grid are substantially equal. After such time, valve 61 will notconduct. It may readily be seen that the weld time or the number of halfcycles during which valve 61 will conduct, is independent of the valueof the voltage to which capacitors 54 and 55 are charged, the weld timeor number of conductive periods being dependent only uponthe time ofdischarge of said capacitors, the time required for the cathode voltageto equal the grid voltage being always the same for any particularsetting of the discharge resistors.

The secondary of transformer 68 is connected in series with capacitor 54in order to help synchroniZe the timing action with the power supplyvoltage wave, while capacitor S4, resistor 65, transformer 62 andrectier 63 serve to provide a hold-off bias for the grid 66 of valve $1.

During weld time, the current conducted by valve 61 energizestransformer 14. The secondary of that transformer charges capacitor 15.The charge on capacitor is oscillatory in form and during the next halfcycle when the anode |23 of valve 16 becomes positive, the charge oncapacitor 15 is positive at the grid end. The hold-off bias is therebyovercome to eiect the conduction ofthat valve.

The current which valve 16 conducts energizes transformer 88 and chargesiiring capacitor 11 through inductive reactor 81 which is tuned forseries resonance with the capacitor 11, the resonant condition servingto charge the ring capaci tor 11 to a voltage substantially greater thanthat of the output of charging transformer 86. Moreover, the inductivereactor S1 tends to limit abnormal current values in the valve 16circuit to safe magnitudes.

The energization of transformer 68 by the conduction current of valve 16causes the secondary of transformer 238 to supply a charge to capacitor||2. The charge is placed upon the capacitor I |2 during the half cyclein which valve 16 conducts, this charge causing valve i|| to conductduring the following half cycle, the conduction of the valve lil servingto charge ring capacitor Il through the reactor |24 tuned to seriesresonance therewith, as previously described for the interaction ofcapacitor 11 and reactor 81.

During the half cycle following that of the conduction of valve 1S, avoltage is supplied to the grid 94 of valve 93 by a secondary of peakingtransformer 99, the voltage peak occurring in an adjustable andpredetermined` position in each half cycle. This selection isaccomplished by the capacitance-resistance bridge combination indicatedgenerally at liii and the adjustment of resistor |62 thereof. This pulseof grid voltage overcomes the hold-off bias, supplied to the grid 94 bythe charge on capacitor 91 supplied by transformer 9F, and causes valveQ3 to conduct, the conduction of this valve serving to rapidly dischargefiring capacitor 11 through the resistor |25, inductive reactor me, andthe igniter 92 of electric discharge tube 9| and the mercury poolcathode thereof. The resistance |62 is adjusted to vary the phase angleof the voltage supplied by a secondary of peaking transformer 93 to thecontrol grid of valve 93 (and by another secondary of the sametransformer to the control grid of valve EBS). The particular point onthe voltage wave at which the peak of positive voltage is supplied fromtransformer S9 to the control grid of valve 93 (and to the control gridof valve |09) determines the length of time during which current can bepassed by the associated electric discharge tube; or, in other terms,the phase angle of the positive voltage supplied by the secondary ofpeaking transformer E9 determines the weld heat by controlling the pointon the supply wave at which current passes to the load. The resistor |25and inductive reactor |26 serve to shape the discharge pulse of firingcapacitor 11 to give proper firing performance.

During the half cycle following that during which ring capacitor |93 wascharged, a secondary of peaking transformer 99 supplies to the controlgrid circuit of valve |59 a pulsed positive ring potential. This occursduring the half cycle immediately following that during which a firingpotential was supplied to the control grid S4 of valve 93. Consequently,valve it?) conducts during the half cycle immediately following thatduring which valve 93 conducted, the conduction of valve |09 serving todischarge ring capacitor |08 through the igniter circuit of electricdischarge tube H33 previously described for the valve 93, firingcapacitor 11, and electric discharge tube 9| arrangement.

It may readily be seen that the initial current through the weldingtransformer |65 during any welding operation is always conducted bydischarge tube 9|, that the nal current through the welding transformerduring any welding operation is always conducted by discharge tube |03,that the polarity of each pulsation of current through the weldingtransformer is opposite to that of the pulsation immediately precedingand following; that welding current ows during even numbers of halfcycles only; and that the flow through the discharge tubes always startsat the same point on the voltage wave for any setting of the phaseshifting selector mi.

During weld time, thecurrent conducted by valve B1 energizes transformer13, as previously explained, which serves to charge capacitor 18 throughrectifier 19. The charge on capacitor 18 is so polarized as to establishat the grid |21 of valve |3 a potential negative with respect to cathode|28 of that valve. Before capacitor 18 had acquired a charge, the grid21 was at such a potential with respect to cathode l 28 that valve |3conducted. The charge on capacitor 18 serves to cut oi conduction ofvalve |3. The grid |29 Ofi? valve; I 3a; being; electrically; connected;to; the plate; I 3 1.; offvalve I 35 thereby becomes 1 more positive;and valve, I3a conductstocharge the holdl time, capacitor I'I'jbyf thegridv conduction ofv 'valve I II.V At therendofthegweld time whenvalve`6l: is ;no1onger` conducting, the pulses ofiv` current. which energizetransformepIB; capacitor'Bgdis.-

charges through the-resistors 8| and 82 valveIS.y

again conducts; and valve |3a. ceasesto conduct'. Thecontrol grid |32of= valve I4 assumes-a nega.- tivefvoltagedue to thegcharge. on the`capacitor IJwhenvalve |3a stops conducting; Valve |4 Willmotconduct'whensubsequently the anode ofi this tube becomes positivey withrespecti. tothe cathodegthereoi untilzsuch time as' the chargeon the capacitor. I 'Iis dissipated. The, dissipation o fithe charge ons capacitor; I 'l isaccomplished through thee adjustable resistor; combination; |152 whichdeterminesthe hold time in the. weld-v ing cycle; When iinally theholdtime= capacitor; I'Iis suiiicientlyA discharged, thegr-id |32 ofVvalve I4 is at a potential'such as to render'thisvalvegconductive,whenlsubsequently the anode of? this Valve is positivewith respect to the cathode thereof. Transformer I 33zis polarizedl andconnected so as to provide aA synchronizing A. C. voltagein theY valveI4: grid circuit. The recti'er bridge 1 provides the anode |311`of'valve I4 with ai. pulsating D. C. voltagein order that the grid |32mayf regainl control over the conduction of this-gaslled valve.

During the periodin4 which valve I4 is-nonconductive, the grid of valve22. is at a` potential with respect to the cathode thereof to cause thevalve 22 to conduct, charging capacitor 23. by gridi conduction of valve25. When valve |4.conducts, however., Valve 22 does notk conduct. Grid|36, now no longer incontact with the positive D. C; voltage through thevalve 22, immediately becomesznegative with respect tocathode |3'l ofthisvalve due to the' charge on capacitor 23; andil subsequent: positive.anode potentialscam. not cause the tube to re. Conductionof currentthroughvalve v25 ceases'and relay` coil 33is there. by deenergized;contacts .35, 34 and36 are opened, contacts. 3'| andi 38. reclose, andthe OFF time period; is begun. Should the initiating switch 32 bekvheld. closed, or should that switch. be reclosed',

thecycle'justi. described is repeated as soon as.

the charge on capacitor 23 is dissipatedrthrough adjustable resistorcombination-. 24,-, permitting the; grid. I36f-of valve 25- to assumeaypotentiall, such that' valve V2 5, conducts.

Thefcycle, will not: repeat;y when the initiating switchA 3 2: is heldlclosed; however,` if thee non.,- repeat: switch 2S is. closed.Y Withthis switcln closed; theyOFF time potentiometer 2ispartiallyshorted-andthe cathode circnit of-,valve;-2. 8; iscompleted,' permitting the Valve;28;' toi conducta afterthe charge onv capacitor 3| has veryfrapidlydissipated. The conductioncurrent of" valve 28; passesV from the positiVefI-. C. supply throughthe relay coil 33; and initiating switch;V32; to; charge. capacitor 2 3, thel charge on the capacitor 233 causingthe-:grid |35 :0f va1vef25 sv to: assume a s0- tentialpsucli that valvey2n5-cannot conduct even. though the initiating. switchisheld closed.When. the/ initiatingi switch. isv opened; valve, 2% ceases; taconduct,the charge G rlY capacitor 'eis dissipated, the charge on Glllfitor;35,is-,reestablished,v and, the. valve 2v5is;in condition; to .YconclucISi-wliell.` the initiating switch isreclosed.

It may be seen 1 that transfrmer: M92 prima-rviseinlserieswith;thethermaliflow'Switghheat Uil, whilethe secondary.of.I transformer II il serves asf the;` powersupply: to;` the. lamentf'.off. the-.relae tivelyA inexpensive rectifiertube` 53i Should the:`thermali ilow. switch heaters' burn out onshore;- out, the secondary of.transformer I'Illzis sonds-.LV posed that the tube 53 will become`inoperative duefv eitherv to lacky of' lament power or-lament burn-out.With tube 53thusly inoperative, the weldV timing capacitors 511 and. 55cannotf bei charged' and the initiation of a weldingperiod isnotpossible. The expensive poWertubesfare,l therefore protected from,`faults. in,- thev. thermal OW switch heaters.

While certain preferredembodiments ofithewinsi vention have beenspecically disclosed, itiiszune, derstood thatthe invention is` notlimited there'.-J to, as many variations,A will be readily. apparenti.to those skilled in the art and theinvention. is; to be given itsbroadest possibleinterpretationz within the terms of the followingclaims:

What is claimed is:

l'. In a system, for the sequencing off Welding.; operations, a pair-ofelectric discharge tubesforf controllingthe passageV of current toawel-dinge load, a capacitor, means for charging-said capace.. itor, anelectric Valve, means. connecting: saidf capacitor to the control'gridofsaid electricvalva, a` Valve solenoid, means energizing said valvesolenoid to apply pressure to thewelding elec-.: trodes, means foreiectively disconnecting saldi capacitor from, said charging. meanstoinitiates the squeeze time period; means incl'uding.-A a.: variableresistor bridging said capacitor toeiect? an adjustabledischargetimelfor said capacitors thereby determining the squeeze timeperiod-, a voltage supply, a capacitor, means foncharging; saidV lastJvmentioned capacitor with onepolarityfy from said voltage supply, meansfor impressingf the voltages of'saidlast mentionedcapacitorfand saidlast mentioned charging means, also. upon.

. the control; grid circuit of. said electricvalve, a

pressure switch responsive to electrode pressureu means for dischargingsaidlast Inentionedzcapace. itor upon closure of said pressure switchtopere. mit the squeeze time timing means-to controlir the conduction ofsaid electric Valve, the/.voltages upon'the grid thereof always beingisuirciently negative toprevent conduction ofsaidvalvefuntil: after theclosure of saidY pressure switch@ and; adjustable timing meanscontrolling the number;- ofzconducting periods of said electricdischarge; tubes, thereby determining the weldtimepeg riod.

2. In a system for sequencing of: weldingl Opie-. erations, a pair ofelectric discharge tubesorr controlling the passage of current to aAwelding load, a capacitor, means for charging said capaceitor, anelectric valve, means connecting said capacitor tov the control grid ofsaid electric; Valve, a valve solenoid, means energizing saint'-v valvesolenoid to applyI pressure to thewelding; electrodes, means foreifectively disconnecting; said capacitor from said charging means; toi.initiate the squeeze time period, means include., ing a Variableresistor bridging said: capacitanE to; effect an adjustable discharge;time for; said capacitorl thereby determining the squeeze time?rtvperiod, avoltage supply, a; capacitor, meanszfor;- charging-said lastmentioned:capacitorswith one; polarityfrom 1 saidV Voltage supply,Imeansjfforfixn-...- pressing the voltages of said last, mentionedcapacitor' and said last mentioned charfgli means also upon the controlgridcllicuit o f saig electricy valve, a pressure switch responsive to;electrode,- pressura means forf disharglllg last mentioned. capacitorupon-4 closure pressure switch to permit the squeeze time" timing meansto control the conduction of said electric valve, the voltage upon thegrid thereof always being suiciently negative to prevent conduction ofsaid valve until after the closure of said pressure switch, adjustabletiming means controlling the number or" conducting periods of saidelectric discharge tubes, thereby determining the weld time period, andadjustable timing means controlling the length of time after thecessation of load current now during which pressure is applied to theWork on the hold time period.

3. In a system for the sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, a capacitor, means for charging said capacitor, anelectric valve, means connecting said capacitor to the control grid ofsaid electric valve, a valve solenoid, means energizing said valvesolenoid to apply pressure to the welding electrodes, means foreffectively disconnecting said capacitor from said charging means toinitiate the squeeze time period, means including a variable resistorbridging saidcapacitor to effect an adjustable discharge time for saidcapacitor thereby determining the squeeze time period, a voltage supply,a capacitor, means for charging said last mentioned capacitor with onepolarity from said Voltage supply, means for impressingY theA voltagesof said last mentioned capacitor and said Ilast mentioned charging meansalso upon the control grid circuit of said electric valve, a pressureswitch responsive to electrode pressure, means for discharging said lastmentioned capacitor upon closure of said pressure switch to permit thesqueeze time timing means to control the conduction of said electricvalve, the voltage upon-the grid thereof always being sufficientlynegative to prevent conduction of said valve until after the closure ofsaid pressure switch, adjustable timing means controlling the number ofconducting periods of said electric discharge tubes thereby determiningthe weld time period, adjustable timing means controlling the length oftime after the cessation of load current ow during which pressure isapplied to the work or the hold time period, and adjustable timing meanscontrolling the period during which the Welder is inoperative or the oitime period.

4. In a system forthe sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, an electric valve, adjustable timing means normallycontrolling the length of time after the initiation of the Weldingsequence until the conduction of said electric valve or the squeeze timeperiod, a voltage supply, a capacitor, means for charging said capacitorwith one polarity from said voltage supply, means for impressing thevoltages of said capacitor and said charging means upon the control gridcircuit of said electric valve, a pressure switch responsive toelectrode pressure, means for discharging said capacitor upon closure ofsaid pressure switch such that the squeeze time timing means controlsthe conduction of said electric Valve, the voltage at the grid thereofalways being sufficiently negative to permit conduction of said valveuntil after the closure of said pressure switch, adjustable timing meanscontrolling the number of conducting periods of said electric dischargetubes thereby determining the weld time period, adjustable timing meanscontrolling the 10 length of time after the cessation of load currentnow during which pressure is applied to the work or the hold timeperiod, and adjustableV timing means controlling the period during whichthe Welder is inoperative or the oi time period. Y

5. In a system for the sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, a capacitor, means for charging said capacitor, anelectric valve, means connecting said capacitor to the control grid ofsaid electric valve, a valve solenoid, means energizing said valvesolenoid to apply pressure to the welding electrodes, means foreffectively disconnecting said capacitor from said charging means toinitiate the squeeze time period, means including a variable resistorbridging said capacitor to eiect an adjustable discharge time for saidcapacitor thereby determining the squeeze time period, a voltage supply,means connecting said voltage supply also to the control grid of saidelectric valve, means including a pressure switch responsive toelectrode pressure associated with said voltage supply, the potential ofsaid control grid always remaining suiciently negative to prevent theconduction of said electric valve until after the closure of saidpressure switch, adjustable timing means controlling the number ofconducting periodsA of said electric discharge tubes, therebydetermining the Weld time period, means energizing said last mentionedtiming means, and thereby initiating the action thereof upon theconduction of said electric valve, adjustable timing means controllingthe length of time after the cessation of load current flow during whichpressure is applied to the work or the hold time period, meansenergizing said last mentioned timing means during the weld time period,means initiating the action oi said last mentioned timing meansimmediately after the ermination of said weld time period, adjustabletiming means controlling the period during which a welding device isinoperative or the off time period, means energizing said off timetiming means during the operative period of said hold time timing means,and means initiating the action of said oi time timing means immediatelyafter the termination of said "hold time period.

6. In a system for the sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, a capacitor, means for charging said capacitor, anelectric valve, means connecting said capacitor to the control grid ofsaid electric valve, a valve solenoid, means energizing said valvesolenoid to apply pressure to the welding electrodes, means foreffectively disconnecting said capacitor from said charging means toinitiate the squeeze time period, means including a variable resistorbridging said capacitor to eiect an adjustable discharge time for saidcapacitor thereby determining the squeeze time period, a voltage supply,a capacitor, means for charging said last mentioned capacitor with onepolarity from said voltage supply, means for impressing the voltages ofsaid last mentioned capacitor and said last mentioned charging meansalso upon the control grid circuit of said electric valve, a pressureswitch responsive to electrode pressure, means for discharging said lastmentioned capacitor upon closure of said pressure switch to permit thesqueeze time timing means to control the conduction of said electricvalve,

the voltage upon the grid `thereof always being suiilciently negative toprevent conduction of said valve untilafter the'closure of` saidpressureswitch; adjustable timing means including a pair of capaci-tors,means for charging said pair of capacitors simultaneously upon theconduction of said electric valve, means effecting the conduction ofsaid electric discharge tubes during a length of time dependent upon thedierence in the rates of discharge of said pair of capacitors,adjustable timing means controlling the length of time afterk thecessation of load current flow during which pressure is-applied to theWork or the ffhold time period, and adjustable timing means controllingthe period during which a Welding device is inoperative or the oi timeperiod. Y

7.- In a system for the sequencing of Welding operations, a pair ofelectric discharge tubes for controlling thepassage of current to awelding load, adjustable timing means controlling the length of timeafter the initiation of the Welding sequence until the initiation of theWeld time period, adjustable timing means controlling the weld timeperiod including apair of capacitors, means for charging said pair ofcapacitors simultaneously, means including a resistor Vparalleling oneof said capacitorsmeans includinga variable resistor paralleling theother of said capacitors to eiTect a diierence between the rates ofdischarge of said capacitors, means including an electric valvecontrolling the conduction of said electric discharge tubes, meansconnecting said electric valve to said pair of capacitors so that theperiod ofV conduction thereof is dependent upon the difference betweenthe rates of discharge of said pair of capacitors, adjustable timingmeans controlling the length of time after the cessation of load currentflow during which pressure is applied to the Work or the hold timeperiod, and adjustable timing means controlling the period during whichaWelding device is inoperative or the off time period.

8. -In a system for the sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, adjustable timing means controlling the length of timeafter the initiation of the welding sequence until the initiation of theWeld time" period, adjustable timing means controlling the "weld timeperiod including a pair Vof capacitors, means for charging said pair ofcapacitors simul-v taneously, means including a resistor paralleling oneof said capacitors, means including a variable resistor paralleling theother of said capacitors to eiTect a diiierence between the rates -ofdischarge vof said capacitors, 'an electric valve, means connecting saidelectric valve to said pair of capacitors such that the period Vofconduction thereof is dependent upon the 'difference in the rates ofdischarge of said pair of capacitors, a second pair lof capacitors,means charging one of said second pair of capacitors subsequent to theconduction of Asaid last mentioned electric valve, means charging theother of said second pair of capacitors subsequent to the charging ofthe rst of said vsecond pair, means connecting one of said second pairof capacitors to the igniter of one of said electric discharge tubes,means connecting the other ofi-said -second pair of capacitors to theother of said electric discharge tubes, means discharging said secondpair of capacitors through the igniters of said electric discharge tubesto initiate the conduction thereof, adjustable timing means controllingthe length of time after the cessation of load current ow during1 whichpressure is applied to the Work orrthe' hold time period, and.adjustable timing means controlling the period 'during WhichV a Weldingdevice is inoperative ,or the off time period.4

v 9. In a system for the sequencing of welding operations, a pair etelectric discharge tubes for controlling the passage of current to aWeld-ing load, adjustable timing means controlling the length of timeafter the initiation of the Welding sequenceuntil the initiation of theweld timef period, adjustable timing means controlling the period duringwhich the electric discharge tubes can conduct or the ,Weld time period,a pair of capacitors, means responsive to the action of said lastmentioned timing means for charging one of said .pair of capacitors,meansfor charging the other of said pair of capacitors subsequent; tothe charging of the rst pair, means for discharge ing said capacitorsthrough the igniters of said electric discharge tubes to eiectconduction therefof, -adjustable timing means controlling the length oftime after the 'cessation of load current flow during which .pressure isapplied to the Work or the hold time period, and adjustable timing meanscontrolling the period .during which a Welding device is inoperative orthe oit time period.

10.. .In a system for the sequencing of Welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, adjustable timing means controlling the length of timeafter the initiation of the Welding sequence until the initiation of theWeld time period, pressure responsive means, means nulli-` fying theeiect of said timing means until after the operation of said pressureresponsive means, adjustable timing means controlling the Weld timeperiod including a pair of capacitors, means for charging said Apair ofcapacitors simultane-- ously, means including a resistor parallelingoneof said capacitors, means including a variable resistor paralleling theother of said pair of ca; pacitors to effect a diierenee between therates of discharge of said capacitors .means including an electric valvecontrolling the conduction of said electric dischar'g'etubes, meansconnecting said last mentioned electric valve to said pair of capacitorssuch that theperiod 'of conduction thereof is Vdependent upon the`difference in the rates of discharge of said pair of capacitors, adjustable timing means controlling the length 1of time after thecessation of load current ilow during which fpressure is applied to thework or the hold time period, fand adjustable timing .means controllingthe periodduring which Aa welding device is inoperative or the off timeperiod.

1l. In a 'system for the sequencing of welding operations, a pair ofkelectric discharge tubes for control-ling the passage 'of current to aWelding load, a capacitor, means for charging said capacitor, an`electric valve, means connecting said capacitor to the 4control gridvof said electric valve, (a valve solenoid., means energizing said valve'solenoid to Vapply pressure to the Weldring electrodes, means 4foreffectively 'discon necta'ng' Asaid' 'capacitor from `said chargingmeans to initiate the squeeze time period, means including a `variableresistor bridging said capacitor to -ieiect` an adjustable vdis*- chargetime for 4said capacitor thereby determining the squeeze time period,adjustable timing 'means l'controlling the Weld time period includ-- ingla pair of capacitors, means for charging said pair'of capacitorssimultaneously, means including a yresistor paralielingone of 'Saidcapacitors,

iiieans including a variable resistor paralleling the other of said pairof capacitors to effect a difference between the rates of discharge ofsaid capacitors, means including an electric valve controlling theconduction of said electric discharge tubes, means connecting said lastmentioned electric valve to said pair of capacitors such that the periodof conduction thereof is dependent upon the diierence in the rates ofdischarge or said pair of capacitors, adjustable timing meanscontrolling the length of time after the cessation of load current flowduring which pressure is applied to the work or the hold time period,and adjustable timing means controlling the period during which awelding device is inoperative or the orf time period.

12. In a system for the sequencing of welding l operations, a pair ofelectric discharge tubes lor controlling the passage of current to awelding load, a capacitor, means ior charging said capacitor, anelectric valve, means connecting said capacitor to the control grid ofsaidv electric valve, a valve solenoid, means energizing said valvesolenoid to apply pressure to the welding electrodes, means foreffectively disconnecting said capacitor from said charging means toinitiate the squeeze time period, means including a variable resistorbridging said capacitor to effect an adjustable discharge time for saidcapacitor thereby determining the squeeze time period, adjustable timingmeans controlling the weld time period including a pair oi capacitors,means for charging said pair of capacitors simultaneously, meansincluding a resistor paralleling one of said capacitors, means includinga variable resistor paralleling the other of said pair of capacitors toeect a diiierence between the rates f discharge of said capacitors,means including an electric valve controlling the conduction oi saidelectric discharge tubes, means connecting said last mentioned electricvalve to said pair of capacitors such that the period of conductionthereof is dependent upon the difference in the rates of discharge ofsaid pair of capacitors, a capacitor, means responsive to the conductionof said last mentioned electric valve to charge said last mentionedcapacitor, a second capacitor, means charging said second capacitorsubsequent to the charging of said last mentioned capacitor, means fordischarging said two last mentioned capacitors through the igniters ofthe said electric discharge tubes to initiate the conduction thereof,adjustable timing means controlling the length of time after thecessation of load current flow during which pressure is applied to thework or the hold time period, and adjustable timing means controllingthe period during which a welding device is inoperative or the oil timeperiod.

13. in a system for the sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, a capacitor, means for charging said capacitor, anelectric valve, means connecting said capacitor to the control grid ofsaid electric valve, a valve solenoid, means energizing said valvesolenoid to apply pressure to the welding electrodes, means foreffectively disconnecting said capacitor' from said charging means toinitiate the squeeze time period, means including a variable resistorbridging said capacitor to effect an adjustable discharge time for saidcapacitor thereby determining the squeeze time period, pressureresponsive means, means nullifying the eiect of said timing means untilafter the operaf 14 tion of said pressure responsive means, adjustabletiming means controlling tlie weld time" period including a pali oi`capacitors, means ioi charging said pair oi' capacitors simultaneously,means including a resistor paraileilng one oi said capacitors, meansincluding a variable resistor paraiieiliig the other oi' said pair oivcapacitors to ellect a oiii'eience between the rates oi discharge ofsaio. capacitors, means including an electric valve controlling theconduction oil said electric discharge tunes, means connecting said lastmentioned electric valve to said pair of capacitors silcn that trieperiod of conduction thereoi is dependent upon tile oiiiereiice in therates or' discharge oi' said pair oi capacitors, ad justable timingmeans controlling the length oi" time arter tile cessation ol loadcurrent now ouring which pressure is applied to the worn or the "holdtime period, anu adjustable timing means controlling the period duringwnicn a welding device is inoperative oi the "oir time period.

la. ln a system Ior the sequencing or welding operations a pair olelectric discharge tunes lor controlling the passage olcurrent to awelding load, a capacitor, means ior charging said capacitor, anelectric valle, means connecting said capacitor to tne control grid orsaio. electric valve, a valve solenoid, means energizing said valvesolenoid to apply pressure to tile welding electrodes, means iorellectively disconnecting said capacitor iroin said charging means toinitiate the "squeeze time period, means including a variable resistorbridging said capacitor to ellect an adjustable discharge time ior saidcapacitor thereby determining the "squeeze time period, adjustabletiming means controlling the weld time" period including a pair orcapacitors, means ior charging said pair or' capacitors simultaneously,means including a resistor paraiieilng one oi said capacitors, meansincluding a variable resistor paralleling the other of said pair ofcapacitors to ellect a diner-ence between the rates of discharge ci'said capacitors, means including an electric valve controlling theconduction ol said electric discharge tubes, means connecting said lastmentioned electric valve to said oi capacitors such that the period ciconduction thereof is dependent upon the diilerence in the rates oidischarge or" said pair of capacitors, a normally conducting electricvalve, adjustable timing means comprising a capacitor and resistor tocontrol the period after the cessation oi' 1load current now duringwhich electrode pressure is applied to the work, an electric valve,means connecting said last mentioned adjustable timing means to thecontrol grid of said last mentioned electric valve to control theconduction thereof, means to interrupt the conduction of said normallyconducting electric valve, means to energize said last mentionedadjustable timing means upon the interruption of said normallyconducting electric valve, means to initiate the timed period controlledby said last mentioned adjustable timing means, and adjustable timingmeans controlling the period during which a welding device isinoperative or the off time period.

l5. In a system for the sequencing of welding operations, a pair ofelectric discharge tubes for controlling the passage of current to awelding load, an initiating switch, a solenoid energized upon closure ofsaid switch, adjustable timing means controlling the length of timeafter the initiation of the welding sequence until the conduction ofsaid electric discharge tubes or the squeeze time period, said timingmeans comprising a capacitor chargedy from a `:source vfand'effectively-clisconnected from said source upon energization of saidsolenoid,`V adjustable timing means controlling the period during-whichsaid electric discharge tubes-can conduct, said lastmentioned adjustable. timing means comprising a pair of--capacitors and meansfor-discharging one,

of-said pair of capacitors-at a-diierent-ra-tefthan that at which theother-ofsaidpair -is discharged,- a normally conducting electric val-ve,adjustable' timing -means compr-ising-a-capacitor and resistor tocontrolthe length of the period after the cessationof load current -ow duri-ngwhich electrode pressure is-applied-to the work, an electric-valve,

means connecting-said last mentioned adjustable timing vmeans -tothe-control grid of -said lastmentioned-electric valve-to-control theconduction thereof, means 4to interrupt the conduction of saidnormally-'conducting electric valve, means to energize said-lastmentioned-adjustable timingAk means uupon the interruption ofsaid-normallyconducting electric valve, means Vto linitiate the timedAperiod vcontrolled sbysa-idlast mentionedadjustable timing means,and-adjustable timing means 'control-ling Athe period during which awelding-device is inoperative or -the -offtime period.

1-6. In a system-for the sequencing-of Welding operations, a pair-,ofelectric discharge tubes forcontrolling-the passage occurrent to-a--weldingload, van initiating switch, -a solenoid -energized uponclosure of saidsw-i-tch, adjustable/timingmeans controllingthe -lengthof time after the initiationof the -welding sequence until theconduction ofsaid electric discharge or the squeeze time period,said-timing means--coznprising -a capacitor charged from -a--source ande-iiectivel-yr during which the Welder is inoperative or the ofi time,an electric valvefmeans connecting said last mentioned adjustable timingmeans in theY control grid circuit'oi said electric valve to control theconduction thereof, a normally vconducting electricvalveymeans-"interrupting the conduction of said normally conductingelectric valve, means energizing said last mentioned timing meansduringY the period in which said normally conducting electricV valve iscut-off, means initiating the timed period determined by said lastImentioned adjustable timing means or the oir time period.

i7. In a system for the sequencing of welding operations, a voltagesupply, a pair or electric discharge tubesl for controlling the passageof current to a welding load, means for adjustably determining thelength of time after the initiation of the welding sequence until theconduction ofV said electric discharge tubes, a first electric valvevle? capacitorsra't different rates, fasecond#electr-ic"v valve having atleast an anode and cathode and a-control electrode, means connectingthe-controlv electrode v-oI'- said second electric valve-to one of` saidpair or capacitors 'and means connecting-the cathode of said secondelectric valve to the other of said pair of capacitors whereby saidsecondr electric valve-'is rendered conductive-'only during: a perioddependent upon the voltage -dii'lerencel between said-capacitors, atransformer having 'al primary -winding and y--a plurality -of secondarywind-ings,- -means connecting the primary fof said4 transformerirl-'circuit kwith said second electric valve, means Vconnecting one ofsaid secondaryA windings -to means for renderingsaid electric dischargetubes conducting during-a weld time* period determined bythe period ofconduction of said second electric valve, a normally conducting thirdelectric valve,- means ror preventing the-v conduction of-said thirdelectric ValVeduringcOn'-` duction of said second electric valveincluding another secondary winding of said transformer, a-i'ourthelectric valve-having a pair of principal electrodes and acontrol electrode, means con-y necting the controll electrode of said-fourth--elecf tric -valve to a potential lower than that oi thecathodeof said fourth electric valve, a third capacitor in the-controlelectrode circuit `of saidv rif-th electric valve, means for connectingsaidthird capacitor ltothe cathode of said fourth electric valve wherebysaid capacitor is charged through control electrode conduction of saidfifth electric-valve yby conduction of said fourth -electricvalve, andan adjustable resistor in parallel with said third capacitor, saidfourth electric valve returning to non-conducting condition-uponreinitiation of conduction of said third electric` valve at thetermination of the weld time period whereby said iifth electric valve isrendered nonconducting for a period determined'by the-rate at which-saidlast-mentioned capacitor discharges` through said-adjustable resistor todetermine'the hold time period.

18. In-asystem for the sequencing-of welding' operations, a voltagesupply, a pair of electric discharge tubes for controlling thepassage-ofV current `toa welding load, means for adjustablydeterminingthe length of time after the initiation of the welding sequence untilthe conduction of said electric-discharge tubes, a rst elec` tric valve'responsive to said last mentioned means, adjustable timing meanscomprising a pair of capacitors, means for charging said pair ofcapacitors simultaneously upon conduct-ion of said electric valve, meansfor discharging each of said pair of capacitors at diierent rates, asecondelectric valve having at least an anode and cathodeV and a controlelectrode, means connecting the control electrode of said secondelectric valve to onev of said pair of capacitors and means connectingthe cathode of said second electric- Valve to the other of said pair ofcapacitorsV whereby said second electric valve is rendered conductiveonly during aperiod dependent upon the voltage difference between saidcapacitors, a transformer having a primary winding and a plurality ofsecondary windings, means connect-- 'ing the primary of said transformerin circuit:

with said second electric valve, means connectingV one of said secondarywindings to means for rendering said electric discharge tubes conductingduring a weld time period determined by the period of conduction of saidsecond electric valve, a normally conducting third electric valve, meansfor preventing the conduction of said third electric valve duringconduction of said second electric valve including another secondarywinding of said transformer, a fourth electric valve having a pair ofprincipal electrodes and a control electrode, means connecting thecontrol electrode of said fourth electric valve to the anode of saidthird electric valve whereby said fourth electric valve is renderedconducting upon the interruption of conduction of said third electricvalve, a normally conducting iifth electric valve having a, pair ofprincipal electrodes and a control electrode, means electricallyconnecting the cathode of said fifth electric valve to a potential lowerthan that of the cathode of said fourth electric valve, a thirdcapacitor in the control electrode circuit of said fth electric valve,means for connecting said third capacitor to the cathode of said fourthelectric valve whereby said capacitor is charged through controlelectrode conduction of said fth electric valve by conduction of saidfourth electric valve, and an adjustable resistor in parallel with saidthird capacitor, said fourth electric valve returning to non-conductingcondition upon reinitiation of conduction of said third electric valveat the termination of the weld time period whereby said fifth electricvalve is rendered non-conducting for a period determined by the rate atwhich said last mentioned capacitor discharges through said adjustableresistorl to determine the hold time period, a normallyl non-conductingsixth electric valve havin-g a pair of principal electrodes and acontrol electrode, means connecting the control electrode of said 18sixth electric valve to the anode of said fth electric valve wherebysaid control electrode of said sixth electric valve acquires a higherpotential during the period of non-conduction of said fifth electricvalve to render said sixth electric valve conductive, a lseventhelectric valve having a pair of principal electrodes and a controlelectrode, a valve solenoid in series with said seventh electric valve,a fourth capacitor in the control grid circuit of said seventh electricvalve and connected to the cathode of said sixth electric valve, meansconnecting the cathode of said seventh electric valve to a potentiallower than that of the cathode of said sixth electric valve, and anadjustable resistor in parallel with said fourth capacitor, said fourthcapacitor charging upon conduction of said sixth electric valve throughcontrol electrode conduction of said seventh electric valve, anddischarging upon the termination of the conducting period of said sixthelectric valve through the adjustable resistor in parallel therewith todetermine the oi time period, said seventh electric valve being cut offduring the discharge of said fourth capacitor.

HARRIS I. STANBACK.

ERNEST G. ANGER.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,295,601 Overbeek Sept. l5, 19422,298,570 Leathers Oct. 13, 1942 2,309,280 Stansbury Jan. 26, 19432,333,363 Callom Nov. 2, 1943 2,390,981 Bivens Dec. 18, 1945 2,459,041Mitsch Jan. 11, 1949 2,476,882 Lexa July 19, 1949

